Arcuate magazine for a firearm and a method for making the same

ABSTRACT

An arcuate magazine for a firearm, such as a rifle or carbine, which has a keyway and follower assembly for delivering rounds of ammunition one at a time to the firing area of the firearm and which may be fabricated from a single piece of metal and have a smooth interior free of welds and rough spots. The invention also includes a method of making such a magazine which includes the steps of deep drawing and wiping the magazine body under substantial pressure using a progressive die having numerous stations.

PRIORITY CLAIM

This application claims priority from U.S. Provisional PatentApplication Ser. No. 60/922,104 filed 6 Apr. 2007, entitled METHOD TODRAW AND FORM A CURVED FIREARM CARTRIDGE MAGAZINE BODY WITH A KEYWAY.

BACKGROUND AND SUMMARY OF THE INVENTION

This invention relates to a cartridge magazine for a firearm and amethod for making such a magazine, and is more particularly related tosuch a magazine and method wherein the magazine is arcuate in shape andhas a body preferably formed from a single piece of metal.

Such a magazine is used to contain ammunition, such as a series ofcartridges, which are fed one at a time by spring means into a firingchamber of a weapon. The spring means maintains pressure on theammunition to force each cartridge in to the firing chamber, and whenspent to deliver the next round into firing position.

An example of a firearm using a magazine is the M16 rifle or carbine,which has become a standard rifle in the United States weapons arsenaland in other western countries. There are several variations of the M16weapon family, such as the M16/A1, A2, A3 and A4, which are the primaryinfantry rifles used by the U.S. military and 15 NATO countries sincethe early 1960s. These weapons use a magazine of the type disclosed inthis application embodying the present invention.

Preferably, such a magazine is arcuately shaped, and has a substantiallyrectangular cross section with parallel opposed longer sides defined bythe height of the cartridge arranged between parallel opposed shortersides defined by the width of the cartridge. One end of the magazine isclosed with a removable base plate, and the other end is open to permita cartridge in juxtaposition to the firing chamber of the weapon to beplaced in firing position. Preferably, such a magazine is fabricatedfrom steel rather than plastic or aluminum, as the magazine is subjectto heat and substantial stress when it is used in the field.

Usually, as in the case of the M16 carbine series, such a magazine isloaded with about 30 shells, weighting about 18 ounces when filled. Sucha magazine must fit into the receiver lower, which is on lower side ofthe weapon, and, so as not to interfere with the operation of theweapon, the magazine is preferably curved toward the barrel relative tothe point of insertion into the firing chamber. Preferably, the magazinehas a keyway formed in one of its thinner sides to train and direct thecartridge in a proper firing position for entry into the firing chamberof the weapon. Conventionally, the magazine is formed by appropriatelybending multiple pieces of metal and spot welding the pieces together.These operations were crucial, because breaking, bending or malformationof the welds or misalignment of the parts could cause the cartridges tobecome canted or in extreme cases to fall from the magazine, making theuse of the weapon ineffective or dangerous in the field. Correctformation of the keyway is critical: a magazine with a misshaped keywaycould make the magazine unuseable as the magazine could not be installedin the receiver lower.

The prior art disclosed a number of magazine structures, such as

Alzamora et al U.S. Pat. No. 7,117,626, which covers a feed lips gaugefor a magazine;

Ciener U.S. Pat. No. 5,461,811, which discloses a machined magazinebody;

Sniezak et al U.S. Pat. No. 5,438,783, which teaches a handgun magazinehaving a slidable butt plate;

Baldus et al U.S. Pat. No. 4,862,619, which defines a cast or moldedencircling element for a handgun magazine;

Chesnut U.S. Pat. No. 4,586,281, for a magazine adapted for use withvarious styles of weapons.

Farrar et al U.S. Pat. No. 4,514,922, which shows a magazine having aspecial latching mechanism;

Weed U.S. Pat. No. 1,400,252, which illustrates a primitive releasingstructure for a magazine. These references cover a long period ofdevelopment of various magazines and features for magazines, but they donot teach the novel construction and methods for fabricating a magazineembodying the present invention which may be used without significantfailures and which is most dependable in the field. Many references inthe prior art deal with magazines for handguns, and these magazines arenot typical of magazines for rifles or carbines, which are subject togreat field stress and situations where the very life of the userdepends upon the effectiveness of the weapon.

Prior art studies of magazines for such rifles and carbines showsignificant failure rates of prior art magazines, sometimes as high as50% or more, but studies of magazines embodying the present inventiondemonstrate almost no failures.

The arcuate magazine device embodying the present invention is strongand fabricated from steel to withstand field stress and has a smoothkeyway and interior permitting free travel of a round from the magazineto the firing chamber of the weapon. These features are accomplished byusing fabrication means which eliminate wrinkles and rough surfaces inthe magazine, as well as selecting welding points which do not interferewith movement of the shell by the magazine follower mechanism.

In the disclosed method the magazine blank is deep drawn from highcarbon steel, preferably having a Rockwell harness of 34-38 RC, so thatthe piece will not bend too easily, but not so hard as to make thematerial brittle. The magazine blank is designed so that only a singleseam is necessary to form it, and so that the keyway is free of welds orwrinkling or similar encroachments. This fabrication requires a metalpressing operation which draws and forms the magazine including thekeyway in a single operation, preferably using a 600 ton press (but alesser press could possibly be used) with an upper pressure pad having amale form arbor, and top male form block and bottom female form block.The top male form arbor presses down on the magazine blank pinchedbetween the upper pressure pad and the lower pressure pad with about5500 lbs. PSI of pressure while the female form arbor resists thedownward draw movement with about 9000 lbs. PSI and thereby forming thekeyway and one of the short sides in the bridge of the magazine. Twolower pressure pads also serve as the curved surface across which theblank is formed as the blank is drawn down between the lower pressurepads. If inadequate pressure is applied, the keyway fails to form. Ifexcess pressure is applied, the metal tears.

Preferably, the male arbor has pilots for locating the watch holes inthe curved side of the magazine blank. These pilot holes preferablyperform the function of keeping the blank in place during the draw andform operation and the wiping operation. Preferably, the edges of theform opposed to the keyway are used to weld close the magazine body bymeans of one or more additive welds, but the position of the weld couldbe elsewhere, so long as it doesn't interfere with the keyway and itdoes not adversely cause wrinkles or rough surfaces on the interior ofthe magazine when formed. This draw and form operation creates amagazine body oriented in the shape of a “U”, with the keyway formingthe base of the “U”. Ribs may be added to the body to remove anywrinkling of the interior of the magazine and these ribs also addstrength to the magazine and support the shell as it moves through themagazine. During the wiping operation, an inner flap is formed and anouter flap is formed running substantially parallel to the keywayenclosing the magazine and in position for welding.

A robotic welder may be used to make the weld on the edges of the blankremote from the keyway, and this weld must follow the curvature of themagazine. After the blank is fully formed and welded into a singlepiece, a spring and follower is inserted into the closed magazine, andthe base plate is applied to close the lower edge of the magazine.

OBJECTS AND ADVANTAGES OF THE INVENTION

It is the object of the invention to provide an arcuate magazine for arifle or carbine of the character described.

Another object is to provide an arcuate magazine which is fabricated inone piece.

Another object is to provide a body for an arcuate magazine which isclosed by additive welds.

Another object is to provide an arcuate magazine for a weapon which maybe heat treated with nitride or the like to provide a hardened finish.

Another object is to provide an arcuate magazine which has asubstantially smooth interior substantially free of wrinkles and roughsurfaces, particularly in its keyway.

Another object is to provide an arcuate magazine which is welded closedon an edge remote from its keyway.

Another object is to provide a method for fabricating an arcuatemagazine which is drawn and formed into a blank having a central keyway,sides depending from the keyway and edges remote from the keyway forwelding the blank closed.

Another object is to provide a method for fabricating a blank for anarcuate magazine having a keyway which is formed and drawn by means ofhigh pressure applied to both sides of the blank.

These and other objects and advantages will become more apparent as thisdescription proceeds, taking in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a perspective view of a part of a M16 weapon having a magazineinserted, with parts broken away to show the interior firing zone.

FIG. 2 is a sectional view of the magazine taken on line 2-2 of FIG. 1and showing the follower mechanism in the center of the magazine.

FIG. 2A is a detailed sectional view of the magazine which shows analternative way for closing the magazine body by welding an edge for theshort side opposed to the keyway over the lower edge of a long side.

FIG. 3 is an elevation view of one short side of the magazine showingthe watch or pilot holes.

FIG. 4 is a sectional view of the magazine taken on line 4-4 of FIG. 3,showing rounds, the follower assembly, the spring, follower housing andribs.

FIG. 5 is an elevational view of one short side opposed to the keywayside shown in FIG. 3, showing the additive welds closing the magazinebody.

FIG. 6 is a schematic view illustrating the stamped blanks being drawnat the draw station. FIG. 6A is a magazine blank not yet drawn butpunched from the sheet metal and then trimmed.

FIG. 7 is a schematic view showing the forming of the drawn blanks.

FIG. 7A is a sectional view taken on line 7A-7A, showing the forming ofthe keyway, taken through a pilot hole.

FIG. 8 is a sectional view showing the cam press putting the ribs andwiping the edge section in the magazine body.

FIG. 9 is a sectional view similar to FIG. 8 showing the cam pressputting the ribs and wiping the edge section on the other side of themagazine body.

FIG. 10 is a schematic view showing the installation of the follower,spring and spring base into the magazine, and the installation of thebase plate.

FIG. 11 is a front view of the draw and form station with the dieclosed.

FIG. 12 is a side view of the draw and form station with the die open.

FIG. 13 is a front view of the wipe station with the die open.

FIG. 14 is a side view of the wipe station with the die closed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS (I) The Magazine

With reference to FIGS. 1-5, a magazine 10 embodying the presentinvention is installed in a rifle or carbine weapon W, in position for around of ammunition to enter the firing area C of the weapon. Theammunition is delivered to the firing area C by means of a spring loadedfollower 11 which travels through the magazine 10 as each round isplaced in firing position.

The magazine 10 is secured in the weapon W in a receiver R and themagazine comprises spaced apart short walls 12 and 13, bridged by spaceapart long walls 14 and 15. One of the short walls 12 has arrangedtherein a keyway 16, and the other short wall 13 comprised of edgesections 17 and 18 which overlap one another and are secured by welds. Aplurality of ribs 19 and 20 are arranged opposed and in line with oneanother in the long walls 14 and 15, and on set of aligned ribs 21 and22 may be larger and deeper than the other sets of ribs. Within theinterior of the walls 12-15, the follower 11 is positioned with a head23, sides 24 and tail 25 slidably engaged in the keyway 16. Preferably,the magazine body is formed in one piece and closed by the additive weldor welds.

As shown in FIGS. 3-5, the magazine 10 has an arcuate shape 26 and onits short walls 12, 13 with side 12 having the keyway 16. Keyway 16 hasa series of watch or pilot holes 27 permitting a view of the cartridgeswithin the magazine. At the end of the magazine 10 remote from thefollower 11 the magazine is closed by a base or floor plate 28. Withinthe interior of the magazine 10, there is a spring 29 secured at one endto a spring base 30 which rests on the base plate 28 and at its otherend to the follower 11 such that the follower is urged by the spring 29to lift the cartridges toward to weapon firing position C. The additivewelds 31 extend along the length of the short wall 13 but leave theinterior of the short wall 12 free of flux and additive material. Theinterior of walls 12-15 and the keyway 16 are substantially smooth andsubstantially without rough spots so that ammunition rounds may beslidably moved by the follower 11 through the magazine 10 to the firingposition C. Alternatively, as shown in FIG. 2A, the short wall 13 a maybe lengthened and a long wall 14 a may be shortened and stepped inwardto permit the edge section 17 a of the short wall 13 a to be folded overthe end of the long wall 14 a and welded in place for closing themagazine 10. FIG. 4 shows the follower 11 partially retracted inmagazine 10 with rounds of ammunition being pushed by the follower 11toward the top of the magazine 10.

Preferably, after the magazine body is fully fabricated, it is heattreated with nitrides. This heat treatment hardens the surfaces of themetal.

(II) The Method of Making the Magazine

With reference to FIGS. 6-10, in a rolled metal sheet 45, a somewhatrectangular magazine blank 40 is formed in the metal sheet 45 bypunching and removing a U-like piece of metal from the metal sheet 45.Prior to the drawing station, pilot or watch holes 27 are formed in thesheet so that they run along the center line of the magazine blank 40perpendicular to the path of travel of the metal sheet 45. The centerline from one edge of the metal sheet 45 across the magazine blank 40including the section with the pilot or watch holes 27 to the other edgeof the metal sheet 45 approximating a bridge 55. The magazine blank 40is connected to the metal sheet 45 by the bridge 55. The pilot or watchholes 27 are in line with the bridge 55. Each magazine blank 40 form hastwo long edges 50, 51 parallel to the bridge 55 and four short sides 60roughly perpendicular to long sides 50, 51. At the draw station, thereis a male form arbor 70. The male form arbor 70 is fitted with pilotpins 80. The pilot pins 80 are set to correspond to the watch or pilotholes 27. When the male form arbor 70 is pressed in a downward directionduring the draw operation the pilot pins 80 go through the magazineblank 40 helping to hold the magazine blank 40 in proper position.During the drawing operation, each short side 60 is angularly bentupwardly. The magazine blank 40 is held in place by an upper pressurepad 90 and lower pressure pad 100. The male form arbor 70 pressesdownwardly while the female form arbor 110 presses upwardly drawing andforming the magazine blank 40. After the drawing and forming operation,the magazine blank 40 has a the keyway 16 with the watch or pilot holes27 running up the middle of the keyway 16. The remaining metal bridge 55connects the magazine blank 40 to the sheet or strip of metal 45 atspans 52, 53.

As shown in FIG. 8, a first pair of short sides 60 are pressed betweenforming blocks 75, 76 so as to add ribs 19, 21 and to wipe over theinterior flap 17. As shown in FIG. 9, a second pair of short sides 60magazine blank 40 is then pressed by another set for forming blocks 85,86 so as to add ribs 20, 22 to the other side of the magazine blank 40and to wipe over exterior flap 18. The action of the press as shown inFIGS. 8 and 9 is bending the long edges 50, 51 at about 90 degrees andforming the ribs 19-21 smooths wrinkles which may have been formed inthe magazine blank 40 and puts the magazine blank in the final shape ofmagazine 10. With reference to FIG. 10, the long side edges 50 and 51are then welded from the exterior of the magazine blank 40 to close themagazine 10. The follower 11 with its head 23, sides 24, spring 29, tail25, spring base 30 are then fitted into the interior of the magazine 10.Finally, base plate 28 is set in place adjacent to spring base 30 toprevent exit of follower 11 and to complete the formation of themagazine 10.

During the drawing and forming operation and the wiping operations, themagazine blank 40 attention is paid to prevent rough surfaces and toinsure that the rounds will travel smoothly through the magazine 10.

The magazine 10 in the preferred embodiment is fabricated in aprogressive die with a series of stations. Preferably, the operationsare as follows:

-   -   1. Pierce the pilot holes 27 into the magazine blank 40. One        would use pressure sufficient to hold the magazine blank 40 and        to strip the magazine blank 40 off the punch, that pressure        being known as stripping pressure.    -   2. Notch the center of the magazine blank 40 using stripping        pressure.    -   3. Trim the ends of the magazine blank 40 using stripping        pressure.    -   4. Draw and form the magazine blank 40 to create the long sides        50, 51 and the short sides 60 using about 5500 lbs. PSI from        above and about 9000 lbs. PSI from below as further explained        below.    -   5. Form the ribs 19-22 and side wipe the top edge of the        magazine blank 40 using sufficient pressure to hold the magazine        blank 40 flat and wiping the edges 50, 51 with minimum pressure        of about 2000 lbs. PSI. The rib forming operation and wiping        operation could be done separately.    -   6. Re-strike the magazine blank 40. The re-strike sets the form        in its finished geometry where male and female form blocks        strike the long and short sides of magazine blank 40 into        magazine 10. Little pressure is required.    -   8. Cut off scrap material.        Wrinkling of the interior of the magazine 10 is also taken out        during the formation of the ribs 19-22, to assure that there are        not rough spots within the magazine body.

The draw and form station used in the method is shown in FIGS. 11-12,using multiple nitrogen cylinders 130 on top and multiple nitrogencylinders 140 on the bottom. The magazine blank 40 is placed the betweenthe upper pressure pad 90 and the lower pressure pad 100 with the maleform arbor 70 above and the female form arbor 110 below. At the momentof the pressing operation, the male form arbor 70 descends and pushesthe female form arbor 110 into a pocket. It is the pocket that wipes thesides. The male form arbor is set in the die. When the die is closing,the upper pressure pad 90 exerts about 5500 lbs. PSI on bottom side formblocks 100. The female form arbor 110 descends and resists that descentwith about 9000 lbs. PSI. Different nitrogen cylinders may be used suchthat they achieve the required pressures. Pressure may be achieved by anumber of means including spring pressure or urethane pressure.Attention should be paid to the travel distance of the cylinders giventhe needs of particular travel distances to do the draw and formoperation to the magazine blank 40. In the preferred embodiment, on topfour Moeller HR2400-125 nitrogen cylinders are used to create about 5500lbs. PSI and on bottom three Moeller HR1500-100 are used to create about9000 lbs. PSI. As depicted in FIGS. 13-14, at the wiping station, thetop nitrogen cylinders 150 are HR 2400-125 and the bottom nitrogencylinders 160 a are Moeller HR1000-100 and 160 b Moeller HR300-100 towipe long side edges 50 and 51. When the die closes, the long side edgesof 50 and 51 are formed over the two form arbors 200. In FIG. 14 thewiping station is shown with the die in the open position. The campushers 210 force the male form arbors toward the center of the die withthe edges 50 and 51 formed over the male form arbors 200, The pressurecreating devices at this station in the preferred embodiment arecylinders that that achieve about 2000 lbs. PSI. Parts 170 a and 170 bare spacers. The magazine is held in the magazine holder 220.

While many changes and modifications can be made in the structure of themagazine and in the method of making it within the spirit of theinvention, it is not intended that the invention should be limited tothe exact structure and steps shown and described.

1. An arcuate magazine for delivering rounds of ammunition one round ata time to the firing chamber of a firearm such as a rifle or carbine,said magazine having a keyway and follower assembly therein for movingsaid round to said firing chamber, said magazine having a one piece bodywith opposed side walls, said keyway being arranged on one of said sidewalls, and welded closure means for said body on another wall remotefrom said keyway.
 2. The arcuate magazine recited in claim 1, whereinsaid body has a smooth interior substantially free of wrinkles and roughspots.
 3. The arcuate magazine recited in claim 1, wherein said body isfabricated from metal.
 4. The arcuate magazine recited in claim 2,wherein said body is formed from a single sheet of metal.
 5. The arcuatemagazine recited in claim 1, wherein said body comprises opposed shortsides and opposed longer sides and said keyway is arranged in one ofsaid short sides.
 6. The arcuate magazine recited in claim 1, whereinthe short side of said body opposed to the side having said keyway hasoverlapping edges welded together for closing said body.
 7. The arcuatemagazine recited in claim 5, wherein a short side of said body opposedto said keyway overlays an edge welded to one of said longer sides. 8.The arcuate magazine recited in claim 5, wherein one of said long sidehas rib means impressed therein and said follower is trained to movethrough said body directed toward said firing area within the confinesof said ribs and keyway.
 9. The arcuate magazine recited in claim 1,wherein said welded closure means comprise additive welds.
 10. Thearcuate magazine recited in claim 1, wherein said keyway has spacedapart pilot holes along and extending through its surface.
 11. Thearcuate magazine recited in claim 3, wherein the surfaces of said bodyare hardened.
 12. A method for making a one piece body of an arcuatemagazine for delivering rounds of ammunition one round at a time to thefiring chamber of a firearm such as a rifle or carbine, said magazinehaving a follower assembly therein for smoothly moving said round tosaid firing chamber, said method comprising the steps of (i) forming ablank by removing opposed inverted spaced apart U-like shaped piecesfrom a strip of metal; (ii) bending the central portion of the stripbetween the legs of said removed U-like shaped pieces toward oneanother; (iii) drawing a keyway into the bridge between said U-likeshaped pieces; (iv) wiping said legs at substantially a 90 degree anglefrom said keyway bridge and bending an edge on at least one of said legstoward the other of said legs, said edge being remote from said bridge;and (v) welding said edge to the other of said legs to form a magazinebody containing opposed shorter sections and opposed longer sections forcontaining said keyway and follower assembly.
 14. The method recited inclaim 12, wherein said bridge has spaced apart pilot holes, and themethod includes the additional step of placing members for holding saidblank in a selected position by means of said pilot holes.
 15. Themethod recited in claim 12, wherein edges of both of said legs are wipedat said 90 degree angle toward one another, so that the edge of one legoverlaps the edge of the other leg.
 16. The method recited in claim 12,wherein said keyway is impressed on its upper and lower surfaces. 17.The method recited in claim 12, wherein ribs are formed during saidwiping, and said wiping removes wrinkles from said blank.
 18. The methodrecited in claim 12, with the additional step of filling said formedmagazine body with a follower assembly comprising a spring, followermember and base plate for urging rounds into said firing chamber. 19.The method recited in claim 12, with the additional step of heattreating said magazine body to harden its surfaces.
 20. The methodrecited in claim 12, wherein said welding step includes adding metallicmaterial during said welding.